System and method for second order multi-layer traffic grooming for optical network optimization

ABSTRACT

A method of automatically generating a computer based layout of an optical communication network is provided. First, communications traffic demand forecast data for an optical communication network is received. Network data corresponding to a deployed optical communication network is also received. Thereafter, a network plan can be automatically generated. The network plan corresponds to a modified network that may be deployed. Also, the network plan can be derived from the network data. Further, the network plan can be constructed in response to the performance of a grooming operation that includes a first level of grooming at an optical level of the modified network and a second level of grooming at an electrical level of the modified network.

FIELD OF THE DISCLOSURE

The present disclosure relates to the design of multi-level transportnetworks.

BACKGROUND

The standards set forth by the Synchronous Optical Network (SONET)define optical carrier (OC) levels and the electrically equivalentsynchronous transport signals (STS) for the fiber-optic basedtransmission hierarchy. For example, an OC-1 is equivalent to an STS-1and provides a data transmission rate of 51.84 Mega bits per second(Mbps). Higher line rates are integer multiples of the base rate of51.84 Mbps. In other words, an OC-3, and the corresponding STS-3, has adata transmission rate equal to 3 times 51.84 Mbps or 155.52 Mbps. Underthe SONET standard, OC-3, OC-12, OC-48, and OC-192 are the most widelysupported fiber-optic rates. However, other rates exist, e.g., OC-9,OC-18, OC-24, and OC-36.

As such, in a telecommunication network, there can be numerous types ofconnections that are established to handle signal traffic at thedifferent transmission rates. These connections can include anycombination of OC-1 connections, OC-3 connections, OC-12 connections,OC-48 connections, and/or OC-192 connections. In order to efficientlyhandle the signal traffic, it is often necessary to groom the signaltraffic traveling over the network. Grooming involves rearranging andrepacking low-speed demand, e.g., DS-1 demand, into higher speedconnections, e.g., STS-1 connections, to obtain high utilization or fillratios. Grooming allows demand from various destinations to be combinedover a single transport connection.

In SONET ring based networks there are two ways to groom demand:centralized ring bandwidth management and distributed ring bandwidthmanagement. In centralized ring bandwidth management, also known as“full hubbing,” all DS-1 demand originating from a node is packed intoone or more STS-1 demands and transported to a central hub node. At thecentral hub node, the incoming STS-1 demands are dropped from the ringand connected to a wideband digital cross-connect system (WDCS). Withinthe WDCS, the individual DS-1 demands are cross-connected to groomedoutgoing STS-1 demands, which are added back to the ring. Then, a numberof co-destined demands can be transported to their common finaldestination.

An alternative to hubbing is distributed bandwidth management. Indistributed bandwidth management, DS-1 demands are routed directlywithin the ring over a shared or collector STS-1. A collector STS-1 isan STS-1 time slot that is accessible by more than one pair of nodes. Inorder to access a collector STS-1, however, an add drop multiplexer(ADM) must be capable of time slot assignment (TSA) at the VT-1.5virtual tributary level.

In a multi-level network, i.e., a network including an electrical leveland one or more optical levels, the concept of traffic grooming, can beused when there is a significant volume of low-speed traffic between twonodes, e.g., central offices (COs). The demand in the multi-levelnetwork can be groomed to share the resources in the electrical andoptical levels, thereby reducing the cost of the network. However, ifeach level is analyzed independently, it is possible that saving costsin one level, e.g., an optical level, can have a negative impact on thecosts associated with the other level, e.g., the electrical level, andvice-versa. On top of this, if a SONET network is already installed inthe field, it is necessary to make use of the SONET network in order toprovide a smooth transition from the installed SONET network to awavelength division multiplexing (WDM) based full optical network.

Accordingly, there is a need for an improved system and method forgrooming traffic in a multi-level network, e.g., during the design of amulti-level network.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is pointed out with particularity in the appendedclaims. However, other features are described in the following detaileddescription in conjunction with the accompanying drawings in which:

FIG. 1 shows the main building blocks for application of a single layergrooming scheme used in a SONET transport network optimization processincluding computer systems that pre-process network data and performnetwork analysis and planning;

FIG. 2 is a diagram representative of three distinct levels of atransport network that can be a candidate for implementation ofmulti-layer grooming approach;

FIG. 3 is a diagram of an embodiment of a second order single layergrooming model;

FIG. 4 is a diagram of an embodiment of a second order multi-layergrooming model;

FIG. 5 is a flow chart to illustrate general operating logic of anembodiment of a grooming tool; and

FIG. 6 and FIG. 7 depict a flow chart to illustrate detailed operatinglogic of an embodiment of a multi-layer grooming tool.

DETAILED DESCRIPTION OF THE DRAWINGS

A method of automatically generating a computer based layout of anoptical communication network is provided. First, communications trafficdemand forecast data for an optical communication network is received.Network data corresponding to a deployed optical communication networkis also received. Thereafter, a network plan can be automaticallygenerated. The network plan corresponds to a modified optical networkthat may be deployed. Further, the network plan can be constructed inresponse to the performance of a grooming operation that includesmulti-layer of grooming at selected nodes of the modified network.

The modified network can include a third node and a fourth node. Thethird node can be coupled to the first node, and the modified networkcan include a first connection between the first node and the thirdnode. Also, the modified network can include a second connection betweenthe first node and the second node and a third connection between thesecond node and the third node. The modified network can also include afourth node and a fourth connection between the second node and thefourth node. And, the modified network can include a fifth connectionbetween the fourth node and the third node. Also, the second node andthe fourth node can be hub nodes.

In this aspect of the present embodiment, the first and secondconnections can be direct connections and the third connection can be a“spoke” connection that connects a regular node to a hub node. The spokeconnection can have a smaller traffic capacity than the directconnections. Specifically, in a SONET network the spoke connection is anSTS-1 connection.

Additionally, in this aspect of the present embodiment, the first nodecan be a central office at a first location and can include an opticaladd drop multiplexer. The second node can be a central office at adestination location and can include an add drop multiplexer. Further,the third node can be a hub that includes a digital cross connect (DCS)and a multi-service transport switch (MSTS) or and optical cross connect(OXC). Finally, the second level of the multi-level network can be aSONET layer and the first level can be an optical communication levelincluding optical add drop multiplexer elements.

In another aspect of the present embodiment, a method of grooming anetwork plan of an optical communication network is provided. A firstset of direct connections can be formed between an origination centraloffice and a destination central office. The set of direct connectionscan include one or more high-speed connections and one or more lowerspeed connection. Next, a spoke connection can be formed between theorigination central office and a hub node. The spoke connection cancarry residual data traffic not carried over any of the directconnections. Moreover, the residual traffic can be groomed with othertraffic and carried together with such other traffic over otherconnections carrying traffic to the destination central office.

In this aspect of the present embodiment, a first cost estimate isdetermined and includes the cost of deploying each of the set of directconnections between the origination central office and the destinationcentral office. Also, a second cost estimate is determined and includesthe cost of deploying each of the spoke connections. An incremental costof a light path to carry traffic from the hub node to the destinationcentral office is added to the cost of deploying each of the spokeconnections. Thereafter, the first cost estimate can be compared to thesecond cost estimate and the lower cost can be selected.

In still another aspect of the present embodiment, a method of groomingmulti-layer traffic is provided and can be used to generate network nodedata, connection data, and wavelength capacity data that corresponds toa combined SONET and wavelength division multiplexed network. Trafficdemand forecast data can be received, and network data is receivedcorresponding to a SONET network and to a wavelength divisionmultiplexed network. Channels of low-speed traffic demand from the SONETnetwork can be aggregated into higher speed connections within thewavelength division multiplexed network to create a network plan for thecombined SONET and wavelength division multiplexed network.

Referring now to FIG. 1, a computer system for executing networkplanning software is shown and is generally designated 2. As shown, thecomputer system 2 includes a microprocessor 4 that has a memory 6, e.g.,a hard disk drive. FIG. 1 shows that the computer system 2 furtherincludes a display device 8, e.g., a monitor, upon which a user can viewnetwork plans developed using the network planning software described indetail below. Additionally, the computer system 2 can include an outputdevice 10, e.g., a printer.

FIG. 1 further illustrates functionality of a non-limiting, exemplaryembodiment of network planning software (S-TOP), designated 12, that canreside within the microprocessor 4, e.g., within the memory 6. Ingeneral, the network planning software 12 includes a data gatheringmodule 14, a data manipulation module 16, a network design module 18,and a validation and reporting module 20. As shown, the network planningsoftware 12 can include a grooming tool 22, e.g., within the datamanipulation module 16, and a network planning tool 24, e.g., within thenetwork design module 18. As described in detail below, the groomingtool 22 can be used to groom, or otherwise transform, network demanddata 26 that is input to the grooming tool 22, e.g., via the datagathering module 14, in order to produce interim demand files 28. Theinterim demand files 28, in turn, can be input to the network planningtool 24 where they are used during the design of a network plan. Asfurther shown in FIG. 1, one or more grooming parameters 30 can be inputto the grooming tool 22 and can be used to determine how the demand data26 is groomed by the grooming tool 22. A description of the groomingtool logic is provided below.

Referring still to FIG. 1, network architecture data 32, such as fiberand system topology data, can be input to the network planning tool 24in addition to the interim demand files 28. Also, as the networkplanning tool 24 is used to design a network plan, a user can make aring topology selection 34 based on the design choices presented by thenetwork planning tool 24. As further shown in FIG. 1, during the designof a network plan by the network planning tool 24, a ring design cycle36 and a robustness testing cycle 38 can be performed. FIG. 1 also showsthat the network planning software 12 can include plural design metrics40 that can be used by the network planning tool 24 during the ringdesign cycle 36. Once the network planning tool 24 has satisfactorilycompleted the ring design cycle 36 and the robustness testing cycle 38,network engineering reports 42 can be created by the validation andreporting module 20 and further, can be output by the network planningtool 24, e.g., via the output device 10. The network engineering reports42 can include STS-1 & OC routing plans.

FIG. 2 shows an embodiment of a multi-level transport network, generallydesignated 50, that can be groomed using the grooming tool 22 describedabove in connection with FIG. 1. As illustrated in FIG. 2, themulti-level transport network 50 can include an electrical level 52,e.g., a SONET level; a first optical level 54, e.g., an optical add/dropmultiplexer (OADM) level; and a second optical level 56, e.g., awavelength division multiplexing (WDM) level 56. FIG. 2 depicts that theelectrical level 52 can include plural electrical nodes 58interconnected to each other. The electrical nodes 58 can include pluralSONET add/drop multiplexer (ADM) nodes, plural digital cross-connectsystem (DCS) nodes, a combination of SONET ADM nodes and DCS nodes, etc.The first optical level 54 can include plural optical nodes 60 that areinterconnected to each other. In one embodiment, the optical nodes 60can include OADM nodes, optical edge device nodes, a combination of OADMnodes and optical edge device nodes, etc. As shown in FIG. 2, the secondoptical level 56 can further include plural optical nodes 62. Theoptical nodes 62 of the second optical level 56 can include pluraloptical cross-connect (OXC) nodes or plural multi-service transportswitch (MSTS) nodes that are interconnected to each other.

It can be appreciated that the interconnection between the electricallevel 52 and the optical levels 54, 56 can be facilitated by specifiednodes, i.e., hub nodes or gate nodes. Further, the gate nodes can havedifferent optical and electrical functionalities. For example, forlow-speed traffic originating in the electrical level 52 to be routedthrough the optical levels 54, 56, electrical-optical (EO) conversionsand optical-electrical (OE) conversions are necessary at designated gatenodes. Between optical nodes 60, 62, high-speed traffic can betransmitted only through optical levels 54, 56. However, the low-speedtraffic between electrical nodes 58 can be transmitted either throughthe electrical level 52 or through the optical levels 54, 56. Thelow-speed traffic demands can be bundled together into higher levelroutes or even light paths, e.g., an OC-48 (2.5 Gbps) connection or anOC-192 (10 Gbps) connection, taking a common route in an optical levels54, 56 thereby reducing costs.

As previously stated, optical-electrical-optical (OEO) conversions areneeded in each designated gate node in order to transfer signals betweenthe electrical level 52 and the optical levels 54, 56. In the presentdisclosure, demand originating in the electrical level 52 can jump tothe optical levels 54, 56 and back, i.e., undergo an OEO conversion, alimited number of times. The intent is to avoid large delays duringtransmission caused by the OEO conversions. Additionally, due to therisk of problems associated with the failure of an OEO converter, alarge number of OEO conversions can have a strong impact on networksurvivability and performance. Each level can provide theprotection/restoration mechanism for the connections that exist in thatparticular level—without exchanging information with other levels.

Typically, when low-speed traffic is groomed into a light path androuted through the optical levels, the intermediate optical nodes cannotaccess the low-speed traffic. If part of the low-speed traffic has to bedropped at an intermediate node, the entire light path is converted toan electrical signal. However, in the new generation of digitalcross-connect systems (DCSs) with optical interfaces, the low-speeddemands can be processed and a new light path can be created to transmitthe remaining demand to the final destination.

Referring now to FIG. 3, an embodiment of a second order single layergrooming model is shown and is generally designated 100. As depicted inFIG. 3, the second order single layer grooming model 100 includes anorigination central office (CO) 102 and a destination CO 104. The secondorder single layer grooming model 100 includes a first hub node 106 anda second hub node 108. Each hub node 106, 108 can include a wide-banddigital cross-connect system (WDCS), which can allow cross-connecting ofthe tributary services at the tributary level and perform trafficgrooming.

FIG. 3 shows that the origination CO 102 can be connected to thedestination CO 104 via a direct CO-to-CO connection 112, e.g., an STS-1connection. The origination CO 102 can also be connected to the firsthub node 106 via a first spoke connection 114, e.g., an STS-1connection. In turn, the first hub 106 can be connected to the secondhub 108 via a hub-to-hub connection 116, e.g., an STS-1 connection.Also, the second hub 108 can be connected to the destination CO 104 viaa second spoke connection, e.g., an STS-1 connection. Finally, FIG. 3illustrates that the first hub 106 can be connected to the destinationCO 104 by a hub-to-CO cross-connection 120, e.g., an STS-1 connection.

It is to be understood that for the second order single layer groomingmodel 100, grooming DS1/VT1.5 demand traffic increases networkutilization efficiency by finding a most economic mix between buildingdirect STS-1 connections between COs or spoke STS-1 connections totransport DS1/VT1.5 traffic to a WDCS located in an intermediate hubnode for grooming with other demands to be sent to the same destination.Further, it is to be understood that there are two distinct decisionthresholds in the second order single layer grooming model 100 shown inFIG. 3. First, there is the origination CO 102 to destination CO 104grooming threshold (TH12az). Second, there is the first hub node 106 todestination CO 104 grooming threshold (TH12hz).

The decision to build a direct STS-1 connection between the originationCO 102 and the destination CO 104 in order to transport a particular setof DS1/VT1.5 end-to-end demands is based on a “TH12az” value. In otherwords, if the demand during a given planning year is more than “TH12az”DS-1s, a direct STS-1 connection is built. On the other hand, the demandlower than the threshold is routed to a WDCS located in a hub node,e.g., the first hub node 106, through an STS-1 spoke connection to begroomed with other demands. Further, if the total demand at the firsthub node 106 exceeds a “TH12hz” threshold value, a hub-to-CO STS-1connection can be built. Otherwise, the demand at the first hub node 106is routed to the second hub node 108 via the hub-to-hub connection 116.

This algorithm can be considered a second order algorithm, since itconsiders two levels of hubbing for each demand. For example, as statedabove, if a first round of grooming of DS-1s in the first hub node 106does not exceed the TH12hz threshold and a hub-to-CO cross-connection isnot justified, the demand is routed to the second hub node 108 using thehub-to-hub connection 116. In one embodiment of the second order singlelayer grooming model 100, the first spoke 114 carries residual or smallamounts of bundled traffic that did not pass the first TH12az thresholdtest. Moreover, in one embodiment of the second order single layergrooming model, the second spoke 118 can be an STS-1 connection betweenthe second hub node 108 and the destination CO 104 and can transportremaining DS1/VT1.5 traffic without a grooming threshold check. In oneembodiment, the second order single layer grooming model 100 can beconsidered “symmetric” if TH12az=TH12hz.

FIG. 4 depicts an exemplary embodiment of a second order multi-layergrooming model, generally designated 150. As illustrated in FIG. 4, thesecond order multi-layer grooming model 150 includes an originationcentral office (CO) 152 and a destination CO 154. Moreover, the secondorder multi-layer grooming model 150 includes a first hub node 156 and asecond hub node 158. As demonstrated in FIG. 4, each CO 152, 154 caninclude a SONET ADM 160, or other type of next generation SONETequipment (NGS), and an OADM 162. Further, each hub node 156, 158 caninclude a WDCS 164 and an MSTS 166 with OXC functionality. It is to beunderstood that the WDCSs 164 and the MSTSs 166 are capable ofmulti-layer grooming in both electrical and optical levels. In thepresent embodiment, the input traffic to the origination CO 152 caninclude DS-1, DS-3, OC-3, OC-12, OC-48 (2.5 Gbps), OC-192 (10 Gb), 1Gigabyte Ethernet (1 GigE), 10 GigE, and transparent wavelengthservices, λ.

It can be appreciated that the second order multi-layer grooming model150 can include an electrical level that is established by theinterconnection of the SONET equipment, e.g., the SONET ADMs 160 and theWDCSs 164. Moreover, the second order multi-layer grooming model 150 caninclude one or more optical levels established by the interconnection ofthe optical equipment, e.g., the OADMs 162 and the MSTSs 166. It canalso be appreciated that a SONET level is capable of transporting timedivision multiplexing (TDM) services such as DS-1, DS-3, OC-3 and OC-12.A WDM optical level is capable of carrying OC-192 (10 Gb), 10 GigE, andtransparent wavelength services, λ. OC-48, 1 GigE, Enterprise SystemsConnectivity (ESCON), Fiber Connectivity (FICON), and Fiber Channelservices can be carried over both SONET and WDM optical networks.

As illustrated in FIG. 4, the origination CO 152 can be connected to thedestination CO 154 via plural direct CO-to-CO connections 168. Thedirect CO-to-CO connections 168 can include, e.g., one or more STS-1connections, one or more OC-3 connections, one or more OC-12connections, one or more OC-48 (2.5 Gbps) lightpath connections, and/orone or more OC-192 (10 Gb) lightpath connections. The origination CO 152can also be connected to the first hub node 156 via a first set of spokeconnections 170, e.g., one or more STS-1 connections. FIG. 4 furtherindicates that the first hub node 156 can be connected to the second hubnode 158 via plural hub-to-hub connections 172, e.g., one or more STS-1connections, one or more OC-48 (2.5 Gbps) lightpath connections, and/orone or more OC-192 (10 Gb) lightpath connections. Also, the second hub158 can be connected to the destination CO 154 via a second set of spokeconnections, e.g., one or more STS-1 connections. Finally, FIG. 4illustrates that the first hub 156 can be connected to the destinationCO 154 by plural hub-to-CO cross-connections 176, e.g., one or moreSTS-1 connections, one or more OC-48 (2.5 Gbps) lightpath connections,and/or one or more OC-192 (10 Gb) lightpath connections.

FIG. 5 illustrates the general operating logic of an embodiment of agrooming tool. Commencing at block 200, network demand data is receivedat the grooming tool 22 (FIG. 1). In one embodiment, the network demanddata can include published network demand data and unpublished networkdemand data. The published demand data, for example, can include DS-1end-to-end speculative forecast for non-switched services with 128, 256,384, 1.5M, 1.5Z, T1, T1ZF, T1ZFN planning groups. Also, the publishednetwork demand data can include DS-3, OC-3, OC-12, and OC-48 highcapacity end-to-end demand with 45M, EC1, SN32, SN33, STN, OC-3, STS3,OC-12, STS-12, OC-48, and OC-192 planning groups. Moreover, thepublished network demand data can include general trunk forecast (GTF)switch services forecasts including message trunk groups, competitivelocal exchange carrier (CLEC) and local number portability (LNP).

Further, a user, e.g., a network planner, can add other required demandsnot included in the published forecasts, i.e., 1 GigE, 10 GigE andwavelength demands. The unpublished network demand data can also includeend-to-end demands representing asynchronous transition plan by route,copper migration plan, dial-for-dial end-to-end demand, and longdistance (LD) demand on interoffice (IOF) transport rings. Theunpublished network demand data can also include broadband demand, e.g.,ATM, frame relay (FR), Internet, video, etc. Additionally, theunpublished network demand data can include customer specific demands,e.g., inquiries on DS-1, DS-3, OC-3, etc.

Continuing the description of the flow chart depicted in FIG. 5, atblock 202, all demands are aggregated. Next, at block 204, all demandsare groomed based on the above-described second order multi-layergrooming model 150 (FIG. 4). Proceeding to block 206, the optimal pathsfor carrying traffic are determined. At block 208, an optimal routingplan including the optimal paths determined above is output. The logicthen ends at state 210.

Referring now to FIG. 6, a flow chart to illustrate detailed operatinglogic of an embodiment of a grooming tool is shown and commences atblock 250, where one or more direct connections are created between anorigination CO and a destination CO. In the present embodiment, thedirect connections can carry a mixture of demand types, and the types ofdirect connections can be based on the “az” thresholds shown in Table 1.For example, if the demand is greater than a TH12az value then a DS-3connection is built. Table 2 shows exemplary values for the “az”thresholds and “hz” thresholds for a symmetrical model. So, based onTable 2, if the demand is given as DS-1 bundles and the number of DS-1bundles exceeds, e.g., twenty (20), then a DS-3 connection can be built.Further, if the demand is given as DS-1 bundles and the number of DS-1bundles exceeds, e.g., sixty (60), then an OC-3 interface is used. Inthe present embodiment, the sequence in which the connections should bebuilt is as follows: OC-192 (10 Gb), OC-48 (2.5 Gbps), and STS-1. Inother words, if the demand traffic calls for an OC-192 (10 Gb)connection, then an OC-192 (10 Gb) lightpath connection should be built

Continuing the description of the flow chart, at block 252, all OC-192(10 Gb) and OC-48 (2.5 Gbps) bundles are set aside. Proceeding to block254, the location of a first hub node corresponding to the originationCO is determined. In one embodiment, the location of the first hub nodecan be based on a user selection and an existing hubbing plan. On theother hand, the direction of each demand can be estimated based on thevertical and horizontal coordinates of the origination CO anddestination CO. Then, the shortest hub location path can be assigned tothe demand. It can be appreciated that, in general, each demand type canhave a different hub location. However, in the present embodiment, it isassumed that the first hub node has the capability and capacity to groomdifferent types of demand in one location.

Moving to block 256, a first set of temporary spoke connections arecreated between the origination CO and the first hub node. In oneembodiment, the temporary spoke connections are STS-1 connections thatcarry residual DS-1 demand from the origination CO to the first hub nodewhere that demand can be groomed with other residual demand, e.g., fromanother origination CO. Once groomed, the demand at the first hub nodemay be large enough to require a direct connection from the first hubnode to the destination CO. Otherwise, a temporary hub-to-hub connectioncan be built from the first hub node to a second hub node and atemporary second spoke connection can be built from the second hub nodeto the destination CO.

Next, at block 258, the cost of direct STS-1 connections between theorigination CO and the destination CO is evaluated for the remainingdemands to determine a first cost. At block 260, the cost of requiredSTS-1 spokes between the origination CO and the first hub node iscalculated. And, the incremental cost of one or more OC-192 (10 Gb)light path and/or OC-48 (2.5 Gbps) light path to carry this and otherremaining demands from the first hub node to the destination CO is addedto that cost to get a second cost. In one embodiment, the sparecapacities of the first set of temporary spoke connections are usedwithout incurring any cost increase. Continuing to block 262, the firstcost is compared to the second cost and the plan with lowest cost isselected. The logic then continues to block 264 of FIG. 7.

At block 264, in the first hub node, all demands destined for thedestination CO are gathered. The connections from the first hub node tothe destination CO are sized using the “hz” threshold values in Table 1and the grooming sequence listed above. Next, at block 266, OC-192 (10Gb) and OC-48 (2.5 Gbps) bundles are set aside to be assigned tolightpaths. Moving to block 268, the cost of direct STS-1 connectionsbetween the first hub node and the destination CO are evaluated for theremaining demands to get a third cost. Then, at block 270, theincremental cost of one or more OC-192 (10 Gb) light paths and/or one ormore OC-48 (2.5 Gbps) light paths plus the cost of required STS-1 spokesbetween the second hub node and the destination CO are calculated forthe remaining demands to get a fourth cost. In one embodiment, the sparecapacities of the second set of temporary spoke connections are usedwithout incurring any cost increase.

Continuing to block 272, the third cost is compared to the fourth cost,and the plan with lowest cost is selected. Thereafter, at block 274, arouting plan based on the lowest costs as determined above is created.At block 276, the routing plan is output. The logic then ends, at state278.

It can be appreciated that the present method is useful for groomingdemand traffic within a multi-level network, e.g., a network having anelectrical level and one or more optical levels. Further, the presentembodiment can enable the development of efficient transition plans fromexisting electrical networks to optical networks. Additionally, themethod according to the present embodiment can enable network designersto assess and evaluate different hubbing and routing methods and then,select the most efficient one. Also, the present embodiment can enablenetwork designers to provide CO traffic requirements for vendors'equipment selection and configuration evaluation. The method disclosedabove can also be used for multi-period planning and network evaluation.

Further, it can be appreciated that by grooming demand traffic using theabove-described invention the number of SONET ADMs required by a networkcan be reduced. As such, the cost of building a network can be reduced.Moreover, the present method can be applied to both ring and meshtopologies having an arbitrary number of nodes under both uniform andnon-uniform, i.e., arbitrary, traffic in order to minimize the costsassociated with ADMs or OADMs.

The above-disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true spirit and scope of the present invention. Thus, to the maximumextent allowed by law, the scope of the present invention is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

TABLE 1 Threshold Values For Multi-Layer Grooming. From DS-1/ DS-3/ ToVT1.5 STS-1 OC-3 OC-12 OC-48 DS-3/STS-1 TH12az, TH12hz OC-3* TH13az,TH23az, TH13hz TH23hz OC-12* TH14az, TH24az, TH34az, TH14hz TH24hzTH34hz OC-48** TH15az, TH25az, TH35az, TH45az, TH15hz TH25hz TH35hzTH45hz OC-192** TH16az, TH26az, TH36az, TH46az, TH56az, TH16hz TH26hzTH36hz TH46hz TH56hz *Interfaces between ADM/NGS, OADM, WDCS and MSTS**Light path connections

TABLE 2 Exemplary Symmetrical Threshold Values For Multi-Layer Grooming.From DS-1/ DS-3/ To VT1.5 STS-1 OC-3 OC-12 OC-48 DS-3/STS-1 20 OC-3* 602 OC-12* 240 9 3 OC-48 (2.5 Gbps)** 960 34 12 3 OC-192 (10 Gbps)** 3840135 45 12 3 *Interfaces between ADM/NGS, OADM, WDCS and MSTS **Lightpath connections

1. A method of automatically generating a computer based layout of anoptical communication network at a network planning computer system,wherein the method is executed from a computer readable storage mediumaccessible to the network planning computer system, the methodcomprising: receiving, at a network planning computer system,communications traffic demand forecast data related to an opticalcommunication network; receiving, at the network planning computersystem, network data corresponding to a deployed optical communicationnetwork; automatically generating, at the network planning computersystem, a network plan corresponding to a modified optical communicationnetwork to be deployed, the network plan derived from the network data,the network plan constructed in response to performing a groomingoperation including a first level of grooming at a first node of themodified network and a second level of grooming at a second node of themodified optical communication network; and providing the network planto a display device; wherein a first threshold is used to performtraffic grooming at the first node and a second threshold is used toperform traffic grooming at the second node.
 2. The method of claim 1,wherein the modified optical communication network comprises amulti-layer network, wherein a first layer of the multi-layer networkcomprises an optical layer and a second layer comprises an electricallayer.
 3. The method of claim 2, wherein the first layer includes dataconnections that operate at a higher transmission capacity thanconnections within the second layer.
 4. The method of claim 3, whereinthe modified optical communication network includes: a third node arid afourth node, the third node coupled to the first node; wherein themodified optical communication network includes a first connectionbetween the first node and the third node, a second connection betweenthe first node and the second node, and a third connection between thesecond node and the third node.
 5. The method of claim 4, wherein themodified optical communication network further includes: a fourth node;a fourth connection between the second node and the fourth node; and afifth connection between the fourth node and the third node; wherein thesecond node and the fourth node are hub nodes.
 6. The method of claim 5,wherein the first and second connections comprise direct connections andwherein the third connection comprises a spoke connection correspondingto a hub and spoke configuration, the spoke connection having a smallertraffic capacity then the direct connections.
 7. The method of claim 6,wherein the spoke connection comprises an STS-1 connection of a SONETnetwork.
 8. The method of claim 1, wherein: the first node is a centraloffice at a first location and includes an optical add drop multiplexer;the second node is provided by a central office at a destinationlocation and includes an add drop multiplexer; the third node isprovided by a hub that includes a digital cross connect (DCS) and amulti-service transport switch (MSTS).
 9. The method of claim 2, whereinthe second layer of the multi-layer network comprises a SONET layer andthe first layer comprises an optical communication layer includingoptical add drop multiplexer elements.
 10. The method of claim 1,wherein the modified optical communication network comprises amulti-layer network, wherein a first layer comprises a first opticallayer, a second layer comprises an electrical layer, and a third layercomprises a second optical layer.
 11. A method of grooming multi-layertraffic to generate network node, connection, and wavelength capacitydata corresponding to a combined electrical and optical wavelengthdivision multiplexed network, wherein the method is executed from acomputer readable storage medium accessible to a network planningcomputer system, the method comprising: receiving, at a network planningcomputer system, traffic demand forecast data; receiving, at the networkplanning computer system, network data corresponding to an electricalnetwork and to an optical wavelength division multiplexed network;aggregating channels of low-speed traffic demand from the electricalnetwork into higher speed connections within the optical wavelengthdivision multiplexed network to create, at the network planning computersystem, a network plan for the combined electrical and opticalwavelength division multiplexed network; and providing the network planto a display device, wherein: a first set of traffic is aggregated at afirst node of the combined electrical and optical wavelength divisionmultiplexed network using a first traffic grooming threshold, and asecond set of traffic is aggregated at a second node of the combinedelectrical and optical wavelength division multiplexed network using asecond traffic grooming threshold.
 12. The method of claim 11, furthercomprising deploying a physical multi-layer network in accordance withthe network plan for the combined electrical and optical wavelengthdivision multiplexed network.